1. Field of the Invention
The present invention relates generally to a temperature control apparatus and method, and a program. In particular, the invention relates to a temperature control apparatus and method that can appropriately perform temperature control on an optical component regardless of the type thereof, and to a program therefore.
2. Description of the Related Art
Apparatuses (e.g. the apparatus described in Japanese Patent Laid-open No. 2005-250249) mounted with components, such as prisms, liquid crystal panels, etc. (hereinafter referred to as the optical components) which operate upon receipt of light have widely been used.
Such optical components are exposed to thermal load resulting mainly from conversion of light into heat. Thus, the optical components have a feature of deterioration due to the thermal load.
On the other hand, it is desirable that the optical components maintain temperatures higher than a certain level in view of performance. In other words, the optical components have another feature in which they do not sufficiently exhibit their optical performance if used at low temperatures.
Because of the two features described above, the optical components need to maintain their optimum temperatures. To meet the need, temperature control has heretofore been performed on the optical components in some cases.
For example, FIG. 1 illustrates an example of the configuration of an existing temperature control system (hereinafter, referred to as the existing system) for performing temperature control on an optical component.
The existing system of FIG. 1 is configured to include an optical component 11 through a temperature regulator 15.
The optical component 11 operates upon receipt of incident light 21 from a light source 12. The incident light 21 serves as a heat source to raise the temperature of the optical component 11.
The existing system of FIG. 1 includes a temperature sensor 13, a controller 14 and a temperature regulator 15, which constitutes a control sub-system (hereinafter referred to as the existing temperature control sub-system) for performing temperature control on the optical component 11.
The temperature sensor 13 is installed in close contact with or around the optical component 11 and senses the temperature of the installation site.
The controller 14 uses the temperature sensed by the temperature sensor 13 to create a command value for the temperature regulator 15. For example, the controller 14 creates, as a command value, a value corresponding to an error (temperature difference) of the sensed temperature relative to a control target value.
The temperature regulator 15 performs operation for raising the temperature of the optical component 11 (hereinafter, referred to as the heating operation) or operation for lowering the temperature of the optical component 11 (hereinafter, referred to as the cooling operation) in response to the command value from the controller 14.
In the present specification, “heating” is a comprehensive concept containing positively applying heat to an object (here, the optical component 11) as well as increasing the temperature of the object to an ambient temperature without application of heat in the case where the temperature of the object is lower than the ambient temperature, for example. In other words, the “heating” simply implicates provision of a factor increasing the temperature of the object. Similarly, “cooling” is an antonym of the “heating” and simply implicates provision of a factor lowering the temperature of the object.
Such an existing temperature control sub-system uses the temperature sensed by the temperature sensor 13 as a feedback value, that is, performs the so-called feedback control so as to eliminate the error (temperature difference) of the sensed temperature relative to the control target value, that is, to make the sensed temperature correspond to the control target value. Specifically, if the error is a positive value for instance, that is, if the sensed temperature is lower than the control target value, a value (e.g. a positive value) instructing the heating operation is given to the temperature regulator 15 as a command value. Thus, the temperature regulator 15 performs the heating operation. In contrast, if the error is a negative value, that is, if the sensed temperature is higher than the control target value, a value (e.g. a negative value) instructing the cooling operation is given to the temperature regulator 15 as a command value. Thus, the temperature regulator 15 performs the cooling operation. When it is judged that the error is zero, that is, when it is judged that the sensed value corresponds to the control target value, for example zero is given to the temperature regulator 15 as a command value. Thus, the cooling/heating operation by the temperature regulator 15 is stopped. This brings the existing temperature control sub-system into a stable state.
As described above, the existing temperature control sub-system uses the temperature sensed by the temperature sensor 13 as the temperature of the optical component 11, sets the optimum temperature of the optical component 11 as the control target value, and performs control to make the sensed temperature correspond to the control target value. In this way, the temperature control is performed on the optical component 11.